1. Field of the Invention
The present invention disclosed in this specification relates to the constitution of an apparatus suitable for generating signals for driving matrix type display devices of various types, display capacities and methods of display (for example, active matrix type liquid crystal display device).
2. Description of the Related Art
In recent years various matrix display devices are known. The most familiar one is a liquid crystal display device in which a simple (passive) display device and an active matrix display device are included. These devices can perform displaying operation by inputting an image signal and a clock (synchronizing) signal from outside. However, in respect of types of signals, there are various types in accordance with display devices and a normal signal needs to be modified and inputted in accordance therewith. This point differs significantly from a cathode ray tube (CRT) which is a typical conventional display device.
For example, an explanation will be given of an active matrix type display device as an example. FIGS. 10A and 10B show a monolithic type active matrix display device having an active matrix portion 84, a data driver circuit 82 and a scan driver circuit 83 on a substrate 81 where these circuits are formed at same plane of the substrate. However, even when the driver circuit is formed by a semiconductor chip, the explanation of the present invention remains unchanged.
The structure designated by FIG. 10A is of the simplest monochromatic display including a synchronizing signal input (CLOCK IN) and a video signal input (VIDEO IN) as input terminals. The structure is similar to that of a normal monochromatic CRT. (FIG. 10A)
Further, as shown by FIG. 10B, the structure of color display is provided with a synchronizing input (CLOCK IN) and video signal inputs (VIDEO IN B, G, R) in correspondence with three primary colors. The structure is similar to that of a normal color CRT. (FIG. 10B)
However, according to a matrix display device, input terminals other than these are provided and therefore, there are devices which need different drive signals.
For example, according to the structure shown by FIG. 11A, although the device is of a monochromatic display, a synchronizing signal input (CLOCK IN) and a first through a fourth video signal input (VIDEO IN 1-4) are provided as input terminals. In a normal CRT, a number of inputs of video signals is only one in the monochromatic display, however, according to a matrix display device, there are cases where the video signal is divided into a plurality of signals in this way which are inputted simultaneously for the purpose of lowering processing speed of signals. (FIG. 11A)
Further, according to the structure shown by FIG. 11B, although the device is similarly of the monochromatic display, a first and a second synchronizing signal input (CLOCK IN 1 and 2) and a video signal input (VIDEO IN) are provided as input terminals. According to a normal CRT, a number of inputs of synchronizing signals is only one, however, in a matrix display device, there are cases where a plurality of synchronizing signals phases of which are shifted from each other in this way are used and signal processing circuits (for example, shift registers 86 and 87) respectively in correspondence thereto are provided for the purpose of lowering processing speed of signals. (FIG. 11B)
Similarly, according to the structure shown by FIG. 11C, a color display matrix having two routes of shift registers and dividing each of image signals in four, is provided with a first and a second synchronizing signal input (CLOCK IN 1 and 2) and a first through a fourth video signal input (VIDEO IN R1-4, G1-4, B1-4) for each of three primary colors. (FIG. 11C)
For example, a data driver of a matrix display device having two routes of shift registers and performing display operation by video signals divided in eight, is provided with the structure shown by FIG. 12. Further, FIG. 13 shows pulse signals (for driving analog sample hold) outputted from shift registers A1 and B1, a video signal before division and signals after division inputted to a first, a fourth and a ninth video signal line. (FIG. 12, FIG. 13)
As described above, according to the matrix display device, various display methods are requested in accordance with the constitution of circuit and the like. Further, there are such a variety of display methods (that is, drive signals) and accordingly, in performing inspection of various matrix display devices, it is necessary to remake circuits for generating drive signals for respective matrix display device. For example, a drive signal suitable for a display device shown by FIG. 10A can not drive the display devices shown by FIG. 11A and FIG. 11B to carry out normal display.
However, to make a drive circuit for each of matrix display devices needs time and expense and hinders efficient operation. The present invention has been carried out in view of the above-described points and it is an object of the present invention to provide an apparatus capable of simply changing necessary drive signals in matrix display devices.